|Year : 2015 | Volume
| Issue : 1 | Page : 76-77
Utility of lead aVR
Vikas Thakran, Anunay Gupta
Department of Cardiology, AIIMS, New Delhi, India
|Date of Web Publication||22-May-2015|
Dr. Vikas Thakran
Department of Cardiology, AIIMS, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
Lead aVR is often overlooked despite multiple clinical uses. Careful attention is required for important diagnostic and prognostic information.
Keywords: acute coronary syndrome, lead aVR, new aVR algorithm, tachycardia
|How to cite this article:|
Thakran V, Gupta A. Utility of lead aVR. J Pract Cardiovasc Sci 2015;1:76-7
Lead aVR is one of the limb leads of augmented electrocardiogram (ECG) leads. It is oriented to "look" at the right upper side of the heart. It provides specific information about the right ventricular outflow tract and basal part of the septum because of its location. It displays reciprocal information covered by leads aVL, II, V5 and V6. It is often ignored, even when considering complex ECGs. As all depolarization is going away, all waves (P, QRS, T) are negative in lead aVR. It is useful in the following conditions:
- In a case of suspected acute coronary syndrome, presence of ST elevation in Lead aVR > 1 mm predicts either left main coronary artery (LMCA) obstruction or proximal left anterior descending artery (LAD) occlusion with severe triple-vessel disease (TVD). The possible mechanism is an infarction of the basal septum and diffuse subendocardial ischemia. While ST elevation in aVR > V1 predicts acute LMCA occlusion, ST elevation in V1 > aVR is more predictive of LAD occlusion usually proximal to first septal branch. In non-ST elevation, myocardial infarction, ST-segment elevation of 0.5 mm or greater in aVR is a predictor of LMCA or TVD with a sensitivity of 76% and specificity of 86%.  ECG shown in [Figure 1] suggests ST elevation aVR lead with reciprocal ST depression in lateral leads. Furthermore right bundle branch block and atrial fibrillation can be noted
|Figure 1: Electrocardiogram showing aVR sign in acute coronary syndrome.|
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- In patients having narrow complex tachycardia, presence of ST segment elevation in lead aVR favors atrioventricular reentry through accessory pathway rather than atrial ventricular nodal reentrant tachycardia as mechanism of tachycardia with a sensitivity and specificity of 71% and 70%, respectively 
- Lead aVR can also be used for differentiating wide complex tachyarrythmia into ventricular tachycardia (VT) versus supraventricular tachycardia (SVT) and aberrancy by use of new aVR algorithm  criteria as described in [Table 1]
|Table 1: Lead aVR criteria suggestive of VT in wide complex tachycardias|
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- Any of the four criteria mentioned in [Table 1] would establish the diagnosis of VT. The overall sensitivity of over algorithm is 96.5% and negative predictive value of 86.6% and flow chart is provided in [Figure 2]
- "aVR sign" is defined as R wave ≥0.3 mV or R/q ≥ 0.75 in lead aVR. It is considered as a risk factor for life-threatening arrhythmic events in patients with Brugada syndrome 
- Reciprocal ST segment depression and PR segment elevation (knuckle sign) in lead aVR are characteristic and help in supporting a diagnosis of acute pericarditis
- In patients with suspected poisoning presence of tall R wave in lead aVR along with the presence of QRS and QT prolongation should suggest the possibility of tricyclic antidepressant poisoning. R wave amplitude >3.0 mm is more sensitive than QRS interval as a predictor of seizures and ventricular dysrhythmias 
- Both dextrocardia and lead reversal (left arm/right arm leads) mimic each other can present with P wave and QRS complex are upright in lead aVR. In case of lead reversal, the precordial pattern (V1 to V6) is normal. With dextrocardia, the QRS voltage gradually diminishes from V1 through V6.
In summary, lead aVR has multiple clinical uses as discussed above. However, in clinical practice while interpreting ECGs, it is often overlooked even by experienced ECG readers. Hence, careful attention to the lead is required, as it provides important diagnostic and prognostic information for both cardiac and noncardiac conditions.
| References|| |
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Liebelt EL, Francis PD, Woolf AD. ECG lead aVR versus QRS interval in predicting seizures and arrhythmias in acute tricyclic antidepressant toxicity. Ann Emerg Med 1995;26:195-201.
[Figure 1], [Figure 2]